Studies are being carried out on primary cultures of astrocytes and on several transformed glial cell lines in vitro. Primary astrocytes are derived from rodents either by viral transformation of primary cultures (HSV-RPA cell lines, S22) or from tumors derived from human pathological specimens, (Mills, Green), or from tumors induced in rodents in situ and subsequently established in vitro, (C6, B9, B82). The levels of key metabolites, glucose, glycogen lactate, pyruvate, ATP, P-creatine, GABA, glutamate, and cyclic nucleotides were measured in cells and medium after refeeding confluent cells with MEM plus glucose. The regulatory enzymes of glycogen metabolism, synthase and phosphorylase have been measured, and the various cell lines have been characterized according to the presence or absence of glycogen and the regulatory enzymes of glycogen metabolism. Primary cultures and HSV-RPA, shown enzyme activities comparable to brain, and a high level of glycogen after addition of glucose. Mills and Green's cell lines shown an unregulated high level of glycogen; and other cell lines, B9, B82, ES22 synthesize relatively low levels of glycogen. These findings are hypothesized to result from the absence of one or both of the regulatory enzymes metabolism.